Lift truck fork operating control mechanism



1965 c. c. BIGLEY ETAL LIFT TRUCK FORK OPERATING CONTROL MECHANISM 2 Sheets-Sheet 1 Filed Feb. 12, 1963 I N VENTOR S FIE: 4 F1 Cl/FFORD C Emmy AMl/EL 6 607719514 2426. FossoM BY Reamer B. S/IVGBQ Zyn %m=rs 1965 c. c. BIGLEY ETAL 3,199,700

LIFT TRUCK FORK OPERATING CONTROL MECHANISM Filed Feb. 12, 1963 2 Sheets-Sheet 2 c INVENTORS Z/FFOED C. Emmy F I 5 SAMUEL H Carma;

faezEC Posse/'4 .BY Reamer B. Sl/VGER W M wars United States Patent 0 3,199,783 LET TRU K FORK @PERA'HNG CQNTR-QL MEQHANZSM (Ilifiord C. lligley, Minneapolis, Samuel El. ottrelh Mound, Earle C. Fossom, Hopkins, and Robert B. Singer, Minneapolis, Minn, assignors to Minneapolis- Moline, inc, Hopkins, Minn, a corporation of Del ware Filed Feb. 12, 1963, Ser. No. 258,975 2 Claims. (Ci. H L-574) The present invention relates to motor vehicles and more particularly to fork lift trucks and to a fork operating control therefor.

In many prior lift trucks, a pair of hydraulic valves are employed for separately actuating a carriage or fork lowerirn and raising cylinder and a fork tilting actuator. Thus, one lever is used to elevate the fork while another is employed for tilting the fork forwardly or rearwardly about a transversely disposed pivot point at the lower end of the rails upon which the fork is carried. This method of operating the valves has, however, resulted in the past in serious accidents on occasion when the fork and rails were tilted forwardly with the fork lifted to its uppermost position and in a fully loaded condition. Under these conditions, with a vehicle on a slight incline grade it is possible for the entire vehicle to topple forwardly. This type of accident ordinarily takes place when an inexperienced operator moves the so-called tilt lever by mistake instead of operating the lower used for lowering the fork.

Attempts have been made to eliminate this potential hazard but the devices employed for accomplislr ng this purpose have never been wholly satisfactory and for various reasons have been, at least to some extent, inefiective in operation.

In view of these and other shortcomings of the prior art, it is one object of the present invention to provide an improved lift truck for operating control wherein a single lever may be employed for both raising and lowering the carriage as well as for tilting the carriage about a transverse axis.

Another object of the present invention is the provision of an improved fork lift truck operating control including a single operating lever and an improved means for returning the operating control to an intermediate position when the lever is released.

A further object of the present invention is the pro vision of an improved lift truck fork operating control including a provision for releasably locking the control lever in selected position and for allowing the control lever to return to an intermediate position from certain other selected positions.

Yet another object of the present invention is the provision of an improved lift truck fork operating control including a provision for reliably preventing the operation of the tilting mechanism while the fork is either being raised or lowered.

Still another object of the present invention is the provision of an improved lift truck fork operating control which is rugged in construction, reliable in operation and can be manufactured at a relatively low cost.

These and other more detailed and specific objects will be disclosed in the course of the following specification, reference being had to the accompanying drawings, in which:

FIG. 1 is a side elevational view of a lift truck embodyin g the present invention.

FIG. 2 is a partial plan View of the forward end of the lift truck of FIG. 1.

FIG. 3 is a partial exploded view of the lift truck fork Bddhjldd operating control mechanism accordin to the present invention.

FIG. 4 is a semi-diagrammatic partial side elevational View of the lift truck fork and fork raising cylinder with the fork in the lowered position.

FIG. 5 is a View similar to FIG. 4 but illustrating the fork in the raised position.

F IG. 6 is an end elevational view of the lift truck fo k operating control according to the present invention.

FIG. 7 is a transverse vertical sectional view taken on line 7-7 of FIG. 6.

FIG. 8 is a horizontal sectional view taken on line 3e of FIG. 7.

FIG. 9 is a schematic diagram illustrating the hydraulic circuit employed in the present invention.

Referring now to the drawings and in particular to F185. 1 and 2, there is shown a lift truck 19 including sides 12, a forward wall 14, rearward wall 16, driven wheels 38 and a steered wheel 20, the latter being suitably mounted for steering movement and operatively connected in any well known manner to a steering wheel 22.

At the forward end of the lift truck it) is a vertically disposed mast including laterally spaced rails 26 of suitable and wel known construction. The lower end of the mast 24 includes a rearwardly off-set portion 28 which is rotatably secured at 39 (P16. 1) for rotation about a transverse axis substantially aligned with the axle of the wheels Suitable actuators 32 and 34 are operative-ly connected to the mast 24- at 36 and 38 for tilting the mast forwardly or rearwardly about an axis 30 to control the inclination of the forks 49 which are suitably mounted for up and down movement upon rails 26. As best shown in FIGS. 2, 4 and 5, an actuator such as a hydraulic cylinder 42 is operatively connected between the forward end of the lift truck and the fork do for raising and lowering the fork it on the mast 24. While the fork 413 can be operatively connected to the cylinder 42 in any of various ways, it is preferably connected by means of a chain 54 which is entrained over suitable sheaves 46 and 43 mounted upon the upper end of the cylinder at the mast, respectively. While one form of fork support structure has been illustrated by way of example, many other types are well known and will be apparent to those skilled in the art.

Referring now particularly to FIG. 9, it will be seen that the lift truck in? also includes a hydraulic fluid pressure pump 5 9 having an inlet line 52 which communicates with a hydraulic reservoir 54. The pump 56 during operation supplies fluid through a pair of outlet ducts and 58 to first and second selector valves 6% and so. The valve so communicates through a line 6 with the cylinder 42 and through a line 66 with the reservoir The valve ea ommunicates through a line 68 with the cylinders 34 and 32 and through a line 79 with the reservoir Thus, during operation, when valve 69 is moved to a first position it will return oil to the reservoir while in the second position it will operate the hydraulic cylinder 52. Valve s2 is a two way valve operating cylinders 32 and 34. While cylinders 32; and 34 have been illustrated as single acting, it is within the scope of the invention to employ double acting cylinders if desired. The improved valve operating control according to the present invention will now be described.

Referring now particularly to FIG. 3 and FIGS. 6 through 8 there is shown a valve operating control mounting plate '72 which is secured to the control panel 74 of the vehicle by means of bolts '76 or other suitable fasteners. The plate 72 includes lever openings 73 and til for levers 82 and respectively. The lever 82 is pivotally mounted upon a transversely extending pin 86 as shown in FIG. 7 and can be employed for controlling the forward or rearward movement of the lift truck it). Since the operation aaoaveo 3 of the lever 32 is not a part of the present invention, no further description thereof Will be presented.

Fositioned laterally of the opening 8:) and extending downwardly therefrom are a pair of parallel bracket plates 38 and 93. Extending between the lower ends of the plates 9i) is a transversely disposed bracket 92'. Rotatably mounted upon the center of the pin 92 is a bracket block 94 which is suitably bored at 9-5 to receive the pin 92. Loosely fitted over the pin 92. on either side of the block 94 is a spacer 98 and mounted for rotation upon the pin 92 laterally of each of the ers 93 are first and second valve operating arms and 232 connected tothe valves 6 and 62 respectively by means of rods M34 and 1 56. The arms tilt) and include centrally extending tabs 163 and 165 respectively as shown in PEG. 3.

As best see in FlGS. 3 and 7, the block is bored at MES to receive a pin used for pivotally securing a generally U-shaped yoke 112 to the block $4. The lower end of the operating lever 84 is suitably connected to the upper end of the yoke 112 as by screw threads 1 34. The yoke 112. thus pivots during the operation about either of the pins 92 or 11% as controlled by the operating lever As best shown in 3 and 8, the opening 30 in the plate 72 includes a pair of parallel slots 116 and 1125 conected at their centers by means of a transverse slot 12%, the movem nt of the ad, of course, b-frg determined by relative pslots 116, 11S and 12%. The slot 13.3 at its upper and lower end includes central notches 122 and 124, respectively, which during operation will function to releasably retain the operating control lever 84 at either of the upper or :lower ends of the slot 113.

Positioned beneath the mounting plate 72 is a resilient biasing member in the form of a generally U-shaped spring 126 which includes a central sharply bent portion 123, a pair or laterally spaced legs 139 and 132 including laterally extending portions 134 and 136 respectively which terminate in loops 133 pivotally secured to the plate 72 by means of two of the bolt 76. To thi end the bolts 76 securing the spring 1.26 to the plate 72 comprise shoulder bolts which function to prevent the loops 133 from being tightly held against'plate 72. Eachsof legs 13% and 132 also include intermediate loops 149 and 142 respectively to provide additional resiliency.

During operation of the lift truck 1%, when it is de sired to raise the forks 40, the lever 84 is moved toward the slot 133 from the central position of lever 84. It is then moved rearwardly until the shaft of lever 84 engages the slot 124. The spring 128 will function to center the shaft 43 within the connecting slot 129' and therefore will also function to urge the shaft of the lever 84 into the notch 12 With the lever 84 in this position, it can be released and yet will remain lodged in the notch 124 until moved by the operator to a new position. The lever 84 can be moved into the notch 12?. and will remain there until released as in the case or the notch 124. However, with the lever 54 in the notch 322, valve 60 will, of course, cause the forks so to be lowered rather than being elevated.

When the lever 84 is moved into the slot 116 it can be moved either forwardly or rearwardly but in either position the spring 12 3 will tend to return the lever to the neutral or central position of FIG. 8.

Since the lever 84 is rigidly connected to the yoke 112, the yoke 112 will move in the direction of the arm 16% when the lever 84 is moved toward the slot 116. As this takes place, the yoke 112 will become engaged over the tab 103 at the upward end of the arm 18%). Ina similar manner when the lever 34 is moved into the slot 113, the yoke 112 will become engaged upon the tab 105 at the upward end of the arm The forward or rear- 1V5. ward movement of the lever 34 in either of the slots 16 or 1115 will thus pivot only one of the arms 1% or 1%2 as the lever is pivoted in an are about the transversely extending bracket pin 92. It should thus be understood that the valves 6t) and 62 can therefore never be operated simultaneously thus reducing the chance of accidents in handling heavy loads. Furthermore, since a single lever is used for both tilting the forks as well as for raising and lowering the forks on the mast, it is impossible for an operator to grasp a lever other than the One intended. The movement of the control lever 84 and the yoke 112 to engage the lever is clearly shown by a dotted line 159 in FIG. 7 while the position of the yoke 11? when in engagement with the arm 192 is shown by a dotted line 1:52 in 1 16. 7.

it is understood that suitable modifications may be made in the structure as disclosed, provided such modifications come within the spirit and scope of the appended claims. Having now therefore fully illustrated and described our invention, what we claim to be new and desire to protect by Letters Patent is:

l. An operating control for a fork lift truck comprising in combination, a mounting plate having an opening therein, supporting means positioned below said opening and movable to a plurality of positions, means within said opening to retain said lever in at least one of said positions, a control means extending through said opening, a yoke mounted upon the lower end of said control means, pivot means at the lower end of said yoke for supporting said yoke upon said supporting means for movement about mutually perpendicular axes at the lower end thereof, laterally spaced means positioned upon either side of said yoke and including portions adapted to selectively engage said yoke when said yoke is moved about one of said axes into proximity therewith, said yoke bein adapted to disengage one of said spaced means when engaged upon the other of said spaced means, each of said spaced means being pivoted about a. second axis positioned at right angles to said first axis, and additional control means operatively connected to said spaced means.

2. In a control for operating two independent valves in a fork lift truck each valve having an actuator arm connected thereto, said actuator arms being mounted in spaced relation for movement about a common axis and having opposing tab portions, a yoke member mounted between said arms for movement on said common axis and an axis perpendicular thereto for movement of the yoke member about said perpendicular axis into selective locking engagement with either tab portion prior to movement about said common axis to move the actuator arm engaged thereby, a mounting plate having an opening therein, a control handle fixed to the yoke and extending through the opening, said opening having an H-shape with parallel leg portions interconnected by a cross portion allowing movement of the lever in the cross portion of the opening about the perpendicular axis to elfect said selective locking engagement and in the leg portions of the opening about the common axis to move the engaged actuator arm, spring means acting between the mounting plate and control handle for yieldably biasing the handle toward a central position about said perpendicular axis, and at least one of said opening leg portions having notches opening away from said central position whereby said spring means will yieldably retain the arm in said positions.

References Cited by the Examiner UNITED STATES PATENTS HUGO O. SCHULZ, Primary Examiner.

MORRIS TEMIN, Examiner. 

1. AN OPERATING CONTROL FOR A FORK LIFT TRUCK COMPRISING IN COMBINATIN, A MOUNTING PLATE HAVING AN OPENING THEREIN, SUPPORTING MEANS POSITIONED BELOW SAID OPENING AND MOVEABLE TO A PLURALITY OF POSITIONS, MEANS WITHIN SAID OPENING TO RATAIN SAID LEVER IN AT LEAST ONE OF SAID POSITIONS, A CONTROL MEANS EXTENDING THROUGH SAID OPENING, A YOKE MOUNTED UPON THE LOWER END OF SAID CONTROL MEANS, PIVOT MEMANS AT THE LOWER END OF SAID YOKE FOR SUPPORTING SAID YOKE UPON SAID SUPPORTING MEANS FOR MOVEMENT ABOUT MUTUALY PERPENDICULAR AXIS AT THE LOWER END THEREOF, LATERALLY SPACED MEANS POSITIONED UPON EITHER SIDE OF SAID YOKE AND INCLUDING PORTIONS ADAPTED TO SELECTIVELY ENGAGE SAID YOKE WHEN SAID YOKE IS MOVED ABOUT ONE OF SAID AXES INTO PROXIMITY THEREWITH, SAID YOKE BEING ADAPTED TO DISENGAGE ONE OF SAID SPACED MEANS WHEN ENGAGED UPON THE OTHER OF SAID SPACED MEANS, EACH OF SAID SPACED MEANS BEING PIVOTED ABOUT A SECOND AXIS POSITIONED AT RIGHT ANGLES TO SAID FIRST AXIS, AND ADDITIONAL CONTROL MEANS OPERATIVELY CONNECTED TO SAID SPACED MEANS. 